The invention concerns a process for the production of a region-wise metallization on a carrier substrate, wherein the carrier substrate is at least region-wise provided with a soluble colored first layer which on its side remote from the carrier substrate is provided over its full area with a metal layer. The invention further concerns a transfer film which includes a carrier substrate and a transfer layer arrangement with a region-wise metallization, wherein the carrier substrate is in the form of a carrier film and the transfer layer arrangement has at least one colored first layer arranged region-wise and a metal layer arranged in coincident relationship with the first layer, as well as the use thereof.
A process of that kind and a transfer film of that kind are known from WO 98/50241. Disclosed therein is a composite film structure which in region-wise manner has a reflecting metal layer which is formed in coincident relationship or in accurate register relationship on regions of a lacquer layer. In that case a carrier film is coated with a soluble, possibly colored first lacquer layer and the side of the first lacquer layer which is remote from the carrier film is covered with a reflecting metal layer. Now, regions of the metal layer are to be removed, by a procedure whereby either a base is applied in a desired pattern to the metal layer or a layer which is insoluble in a base is applied in a pattern to the metal layer and then a base is applied to the insoluble layer and the regions of the metal layer, which have remained free. The base is now said to dissolve the soluble first lacquer layer through the metal layer. It has proven to be extremely difficult however to dissolve the first lacquer layer reliably and completely in the desired regions in that way. The reason for that appears to be due to the applied metal layer which is usually formed by way of a PVD process (physical vapor deposition), generally by means of vapor deposition or cathode sputtering on the first lacquer layer. At least in the region of the surface of the first lacquer layer which is in contact with the metal layer formed, that results in a change in the chemical structure of the first lacquer layer, which has the consequence that the previously base-soluble first lacquer layer becomes insoluble for the base at least in region-wise manner and thus prevents or gives rise to difficulty in structuring of the metal layer.
It is known from DE 102 56 491 A1 for a metal layer to be partially coated with an etch resist lacquer and for the exposed regions of the metal layer to be removed by etching in order to produce a region-wise metallization. It is further disclosed for a soluble lacquer layer to be applied region-wise to a carrier substrate, for a metal layer to be arranged over the lacquer layer and the regions of the carrier substrate which are free thereof, and for the lacquer layer then to be dissolved in order to produce a region-wise metallization on the carrier substrate.
In addition described there is a process in which a soluble lacquer is printed upon region-wise with a hardening agent, the hardening agent and regions of the lacquer which are free thereof are coated with a metal layer and then the lacquer is dissolved in the regions in which there was no hardening agent, including the metal layer disposed thereon, thereby to produce a region-wise metallization of the carrier substrate in accurate register relationship with the hardened regions of the lacquer. As already described hereinbefore those two processes as last described, when using a large number of lacquers, have the consequence that the solubility of the lacquer layer is markedly worsened after the metallization operation so that definedly dissolving away the lacquer layer regions which were provided directly with the metal layer is made difficult or even impossible.
It is further described that a soluble first color or lacquer layer is applied to a carrier substrate over the full area and partially covered with a second color or lacquer layer containing a hardener for the first layer. The regions of the first layer in which the second layer was not present are dissolved by a solvent so that regions with two color layers in accurate register relationship are formed.
DE 34 30 111 C1 discloses a film having a decorative metal layer and a process for the production thereof. In that case, a soluble lacquer on a carrier film is printed upon in region-wise manner with a hardening agent or a hardening lacquer containing a hardener in excess. The hardener diffuses into the subjacent soluble lacquer and hardens it. In that case a concentration gradient of the hardener is produced in the soluble lacquer, wherein the level of hardener concentration decreases in the direction of the carrier film and hardening of the soluble layer to locally different degrees is implemented thereby. In that way, unhardened regions of the soluble lacquer can be present in the region of the carrier film and are also entirely or partially also dissolved away when washing off the regions which were not printed upon with hardening agent. However even if hardening of the soluble lacquer in the region of the carrier film is sufficient to provide that solubility is no longer involved, the irregular hardening of the soluble lacquer, which occurs by virtue of the concentration gradient, has a detrimental effect on its mechanical properties. Furthermore a residue of the pure hardening agent (or however the hardening lacquer) always remains behind at the surface of the previously soluble lacquer and is thus between the metal layer and the previously soluble lacquer. That can result in inadequate adhesion of the metallization.